[PATCH v4 3/3] selftests/udmabuf: Add a test to pin first before writing to memfd

[Vivek Kasireddy <vivek.kasireddy@intel.com>]

Unlike the existing tests, this new test will create a memfd (backed
by hugetlb) and pin the folios in it (a small subset) before writing/
populating it with data. This is a valid use-case that invokes the
memfd_alloc_folio() kernel API and is expected to work unless there
aren't enough hugetlb folios to satisfy the allocation needs.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Steve Sistare <steven.sistare@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
---
 .../selftests/drivers/dma-buf/udmabuf.c       | 20 ++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/drivers/dma-buf/udmabuf.c b/tools/testing/selftests/drivers/dma-buf/udmabuf.c
index 6062723a172e..77aa2897e79f 100644
--- a/tools/testing/selftests/drivers/dma-buf/udmabuf.c
+++ b/tools/testing/selftests/drivers/dma-buf/udmabuf.c
@@ -138,7 +138,7 @@ int main(int argc, char *argv[])
 	void *addr1, *addr2;
 
 	ksft_print_header();
-	ksft_set_plan(6);
+	ksft_set_plan(7);
 
 	devfd = open("/dev/udmabuf", O_RDWR);
 	if (devfd < 0) {
@@ -248,6 +248,24 @@ int main(int argc, char *argv[])
 	else
 		ksft_test_result_pass("%s: [PASS,test-6]\n", TEST_PREFIX);
 
+	close(buf);
+	close(memfd);
+
+	/* same test as above but we pin first before writing to memfd */
+	page_size = getpagesize() * 512; /* 2 MB */
+	size = MEMFD_SIZE * page_size;
+	memfd = create_memfd_with_seals(size, true);
+	buf = create_udmabuf_list(devfd, memfd, size);
+	addr2 = mmap_fd(buf, NUM_PAGES * NUM_ENTRIES * getpagesize());
+	addr1 = mmap_fd(memfd, size);
+	write_to_memfd(addr1, size, 'a');
+	write_to_memfd(addr1, size, 'b');
+	ret = compare_chunks(addr1, addr2, size);
+	if (ret < 0)
+		ksft_test_result_fail("%s: [FAIL,test-7]\n", TEST_PREFIX);
+	else
+		ksft_test_result_pass("%s: [PASS,test-7]\n", TEST_PREFIX);
+
 	close(buf);
 	close(memfd);
 	close(devfd);
-- 
2.49.0